[FIX] web_editor: restore iframe editor code view mode

Broken since https://github.com/odoo/odoo/commit/2972976962617d4b8a0113bae58c640ab41cdff8

addons/web_editor/static/src/js/iframe.js

@@ -56,7 +56,10 @@ editor.Class.include({
 });
 
 rte.Class.include({
-    config: function ($editable) {
+    /**
+     * @override
+     */
+    _getDefaultConfig: function ($editable) {
         var config = this._super.apply(this, arguments);
         if ($.deparam($.param.querystring()).debug !== undefined) {
             config.airPopover.splice(7, 0, ['view', ['codeview']]);